1. Field of the Invention
The present invention relates generally to axial compressors for gas turbines and industrial applications, and in particular to an axial compressor having high-performance airfoils.
2. Description of the Related Art
NACA 65 series airfoils have heretofore been applied to subsonic airfoils located on the downstream side in an axial compressor. As described in “Aerodynamic Design of Axial-Flow Compressors”, National Aeronautics and Space Administration, 1965, (NACA, SP-36), the NACA 65 series airfoils are developed by an organized and comprehensive experimental research using a Wind Tunnel. In recent years, axial compressors have required higher loading combining a higher pressure ratio with cost reduction resulting from a reduction in the number of stages. A subsonic airfoil in the downstream stage of a high loaded compressor increases a secondary flow due to the growth of an endwall boundary layer. Therefore, corner stall occurs on a blade surface, so that a conventional airfoil may provably increase a secondary loss. The application of a high performance airfoil that can control the corner stall is an important technology to improve the performance of a high loaded compressor.
JP,A 8-135597 discloses a method of controlling a secondary flow in an axial compressor. This method involves adjusting the shapes of airfoil end portions liable to cause a secondary flow. Specifically, the method involves adjusting a curvature radius of an airfoil centerline at a position close to the leading edge and at a position close to the trailing edge, with the position of the leading edge of the airfoil remaining fixed, so as to reduce a static pressure gradient on a pressure surface and on a suction surface.